Perpendicular recording has been developed in part to achieve higher recording density than is realized with longitudinal recording devices. A PMR write head typically has a main pole layer with a small surface area at an ABS, and coils that conduct a current and generate a magnetic flux in the main pole that exits through a write pole tip and enters a magnetic medium (disk) adjacent to the ABS. The flux is used to write a selected number of bits in the magnetic medium and typically returns through a write shield structure to a back gap connection that connects the main pole with the write shield structure. In some cases, the write shield structure may allow two return pathways where a portion of the magnetic flux from the magnetic medium passes through a write shield and then through the PP3 trailing shield, and a second magnetic flux portion may pass through a leading shield and a return pass shield (RTP) above a read head that is formed below the write head in a combined read-write structure. A PMR head which combines the features of a single pole writer and a double layered medium (magnetic disk) has a great advantage over LMR in providing higher write field, better read back signal, and potentially much higher areal density.
Unfortunately, not all of the magnetic flux returning to the write head from the magnetic medium follows the preferred pathways mentioned above. PMR writers often include side shields adjacent to the main pole layer and separated therefrom by a side gap dielectric layer. It is believed that the root cause of STE is characterized as flux from the main pole tip going into the magnetic medium and returning to the side shield bottom corners and inner edges that adjoin the side gap. Both bit error rate (BER) and noise amplitude based STE measurements indicate the side writing fields are strong at these side shield bottom corners and inner edges. In general, STE is defined as adjacent track erasure for tracks located more than 0.1 microns from a center track position.
Perpendicular magnetic recording has become the mainstream technology for disk drive applications beyond 150 Gbit/in2. As the demand for high data rate (HDR) drives based on PMR head technology has increased, STE robustness becomes more and more important in order to minimize +/−2 track and beyond bit error rate (BER) loss and servo erasure when multiple writing up to 100kX is applied. With the growing demand for cloud storage and cloud-based network computing, high and ultra high data rate recording becomes important for high-end disk drive applications. Thus, it is essential to design a PMR writer that can achieve high area density capability (ADC) in addition to improved STE robustness.